Preparation Of Biomass Porous Phase Change Materials And The Research Of Thermal And Moisture Properties

In this study, waste walnut shells(a common biomass material) were chosen for raw materials and made into porous materials by means of chemical activation and physical activation(microwave steam heating). After that, two kinds of phase change materials(paraffin,decanoic acid))were combined with this porous material respectively to prepare porous phase-change material by employing vacuum immersed method.The pore size, morphology and structure of the porous materials made from walnut shells and the porous phase-change composites were characterized by automatic specific surface area and pore size analyzer, scanning electron micrograph(SEM), fourier transform infrared spectrometer(FTIR). The aperture test results showed that: porous activated carbon treated with activator had better developed pore structure than those without any processing, which meant specific surface area and pore volume were greatly increased. Morphology test results showed that: porous activated carbon treated with activator presented complex network structure possessing good pore structure. Furthermore, the phase change materials in porous phase-change composites were absorbed in or around the holes of porous active carbon. Considering from the structure test results, there were carboxyl, hydroxyl, ether-base and other functional groups on the surface of porous active carbon treated with activator, whose presence contributes to its adsorption capacity.Secondly, thermal analyzer, constant temperature and humidity box and other testing instruments were chosen to measure the thermal and moisture properties of porous phase-change composites. The results about thermal performance showed that: porous phase-change composites had appropriate phase change temperature and phase change latent heat.The phase transition temperature and the phase change enthalpy in the melting process and the solidfication process was 28.15? and 34.05?, 66.45J/g and 65.5J/g respectively. Moreover, it was clear that porous phase-change composites possessed fine moisture absorption performance according to the results of saturated salt solution test and constant temperature and humidity box test. When relative humidity reached the peak, the maximum of balance moisture absorption was 0.3509g/g. On the other hand, if relative humidity decreased to the least value, the maximum of balance moisture absorption was 0.3519g/g.At last, the gypsum based phase-change composites were prepared by combining porous phase change materials with gypsum materials. Its thermal and humidity performance was then tested and the results showed that: the absorption and liberation ability of heat and moisture of gypsum based phase-change composites was strengthened with the increment of porous phase-change composites. In this paper, a brief discussion for temperature and humidity regulating mechanism of the gypsum based phase-change composites was carried out.